In a conventional recordable optical disc using a red laser, an organic coloring material is used for a recording layer.
However, there is no proper organic coloring material capable of receiving a blue laser in a recordable optical disc using a blue laser, so that use of an inorganic material is examined.
In the case of using an inorganic material, it is proposed to form a recording layer by a multilayer film in order to obtain sufficient reflectance and release heat generated by laser irradiation (refer to, for example, patent document 1).